1. Field of the Invention
The present invention relates to the field of flat panel display, and in particular to a method for inspecting packaging effectiveness of an OLED panel.
2. The Related Arts
A flat panel display has a variety of advantages, including thin device body, reduced power consumption, and being free of radiation and is widely used. Flat panel displays that are currently available generally include liquid crystal displays (LCDs) and organic light emitting displays (OLEDs).
The OLEDs, which show the characteristics of self-illumination, high brightness, wide view angle, high contrast, flexibility, and low energy consumption, attract wide attention to serve as the next-generation display measure that gradually substitute the conventional liquid crystal display devices for applications in mobile phone screens, computer monitors, and full-color television. The OLED displaying, which is different from the conventional way of displaying with LED, requires no backlight and adopts extremely thin layers of organic coatings and glass substrates. These organic materials become luminous when electricity is conducted therethrough. However, the organic materials can get readily oxidized with water and consequently, an OLED display panel, which is a display device manufactured based on the organic materials, must be subjected to extremely severe standard of packaging. For commercial applications, an OLED component must be capable of providing a lifetime exceeding or equal to 10,000 hours and meeting the packaging requirements of water permeability less than or equal to 10−6 g/m2/day and oxygen permeability less than or equal to 10−5 cc/m2/day (1 atm). This infers that packaging is the most important step of the entire process for manufacturing an OLED display panel and is the key factor that affects the product yield rate.
However, only a few methods are currently available to monitor packaging effectiveness achieved in most of the known OLED panel manufacture processes. One of the known processes is one that uses a desiccant to monitor the packaging effectiveness, of which the operation principle is that the desiccant, when absorbing humidity, gets expanded and photographing is applied to identify the surface areas of the desiccant at a preceding and a subsequent time point, whereby the sizes of the surface areas of the desiccant can be used to determine if the desiccant has been expanded and thus if there is any moisture invasion resulting from poor packaging of the OLED panel. The process is simple in principle bur suffers reliability issue. For example, when the desiccant absorbs moisture and gets expanded, the photographing measure only reflects the variation of the surface area thereof, but comparing the images obtained through photographing cannot reflect a minor volume change caused by the desiccant absorbing moisture. Thus, using the measure of desiccant absorbing moisture and getting expanded to inspect the effectiveness of packaging still needs further improvement.
In view of the above shortcomings, as shown in FIG. 1, a method for inspecting packaging effectiveness of an organic light-emitting diode has been proposed, in which a test strip 4 is included in an enclosed chamber 11 collectively formed by a substrate 1, a lid 2, and a sealing layer 3. The enclosed chamber 11 also receives therein a light-emitting chip 9 mounted on the substrate 1. The test strip 4 is attached to the lid 2 to oppose the light-emitting chip 9. Two ends of the test strip 4 are respectively provided with test electrodes 5. An end of the test electrode 5 is connected to the test strip 4 and another end extends to the outside of the enclosed chamber 11. The test strip 4 is generally made of a metallic material that is readily subject to oxidation, such as calcium and barium. The effectiveness of sealing of the enclosed chamber can be determined according to the variation of resistivity caused by oxidation of the test strip 4. The greater the variation of the resistivity is, the better the result of inspection will be.
This method, although effective in identifying the effectiveness of packaging of the organic light-emitting diode, is of a complicated process and a relatively high cost. Further, since the test strip is arranged opposing the light-emitting chip, certain issues, such as contamination of the light-emitting chip and conductivity of the light-emitting chip, may arise from bulging of the test strip.